<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Activation Object</title>
</head>

<body>
    <script type="text/javascript">
        function fn(a) {
            //第一
            console.log(a);
            //第二
            var a = 666; //局部变量
            console.log(a);
            //第三
            function a() {}
            console.log(a);
            //第四
            var b = function() {};
            console.log(b);

            function c() {}
        }
        fn(1);
    </script>
</body>

</html>